What the evidence says about global warming — part three
- Editorial Team SDG13
- 2 days ago
- 6 min read
Published on 22 July 2026 at 02:53 GMT
By Editorial Team SDG13
Science is often portrayed as a search for certainty. In reality, its strength lies in something rather different: the ability to distinguish between what is well established, what is probable and what remains uncertain.
Climate science is no exception.
Much of the public debate surrounding global warming has become polarised between two opposing narratives. One suggests that the science is settled to the point where no meaningful questions remain. The other argues that because uncertainties still exist, the entire body of evidence should be viewed with suspicion.
Neither position accurately reflects how science works.
The scientific method does not require absolute certainty before reaching conclusions. Nor does the existence of uncertainty invalidate decades of observation. Instead, scientific confidence grows as independent evidence continues to support the same explanation while competing hypotheses become increasingly difficult to reconcile with the observations.
That is precisely where climate science stands today.
What scientists know with high confidence
One of the most important contributions of the Intergovernmental Panel on Climate Change (IPCC) has been its systematic approach to evaluating confidence.
Rather than presenting every conclusion with equal certainty, the IPCC assesses the quality of available evidence, the level of agreement across the scientific literature and the remaining sources of uncertainty.
Some conclusions now carry what the Panel describes as very high confidence or are considered unequivocal.
Among them are several fundamental observations.
The Earth’s surface has warmed substantially since the late nineteenth century.
The oceans have absorbed most of the excess heat accumulating within the climate system.
Global mean sea level has continued to rise.
The widespread retreat of glaciers has been documented across much of the world.
Atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased to levels unprecedented in at least hundreds of thousands of years.
Perhaps most importantly, the IPCC concludes that human influence has unequivocally warmed the atmosphere, ocean and land.
This conclusion is not based upon a single dataset, one climate model or one research institution.
It emerges from the convergence of atmospheric physics, oceanography, glaciology, chemistry, satellite observations, paleoclimate research and direct instrumental measurements collected over many decades.
Where uncertainty still exists
Scientific confidence does not imply complete knowledge.
Some of the most active areas of climate research continue to involve questions that remain only partly resolved.
One concerns climate sensitivity — the amount of warming expected in response to a sustained increase in atmospheric greenhouse gas concentrations.
Although the likely range has narrowed considerably over recent decades, researchers continue refining estimates using improved observations, climate models and paleoclimate evidence.
Clouds remain another important source of uncertainty.
Clouds can both cool and warm the planet depending on their altitude, thickness, composition and geographical distribution. Predicting how cloud systems may change under continued warming remains one of the most technically demanding challenges in climate modelling.
Regional projections also remain more uncertain than global averages.
Scientists can estimate with considerable confidence that the planet will continue warming if greenhouse gas concentrations continue increasing. Predicting precisely how rainfall patterns, drought frequency or storm behaviour will evolve in one particular region is considerably more complex.
Large ice sheets also continue to present significant research challenges.
Greenland and Antarctica contain enough frozen water to influence global sea level over centuries. Understanding exactly how rapidly parts of these ice sheets may respond to continued warming remains an active field of investigation.
These uncertainties should not be misunderstood.
They concern the scale, timing and regional expression of future changes.
They do not overturn the extensive observational evidence describing changes that have already taken place.
Why climate models matter
Climate models have become one of the most visible aspects of climate science and, consequently, one of the most frequently misunderstood.
A climate model is not a prediction machine.
It is a mathematical representation of the physical processes governing the atmosphere, oceans, land surface and ice.
Scientists use models not because observations are insufficient, but because observations describe the past and present, whereas models allow researchers to explore how the climate system might respond under different assumptions.
No individual model reproduces reality perfectly.
That is why climate scientists rarely rely on one model alone.
Instead, they compare ensembles of models developed independently by research centres around the world. They evaluate how well those models reproduce historical observations and examine where different models agree or diverge.
This process has steadily improved over successive generations.
Many broad projections made several decades ago regarding long-term warming have proved broadly consistent with subsequent observations, although some regional details have naturally evolved as both observations and computing power have improved.
Models are therefore best understood not as crystal balls, but as tools for testing scientific understanding against the laws of physics.
From evidence to action
Scientific understanding does not automatically determine public policy.
Knowing that greenhouse gas emissions influence the Earth’s energy balance does not answer questions about how rapidly countries should reduce emissions, which technologies deserve greater investment or how the financial burden of transition should be shared.
These are political and economic choices.
Science can evaluate likely consequences.
It cannot decide which values society should prioritise.
Recognising this distinction is increasingly important.
Public debate often confuses disagreement over policy with disagreement over evidence.
One may support nuclear energy while another prefers renewable technologies.
Some favour carbon pricing; others advocate technological innovation or adaptation strategies.
Reasonable people may disagree over these choices.
Such disagreements do not alter the underlying observations describing how the climate system is changing.
Organisations helping society understand the evidence
Two organisations illustrate how climate knowledge is transformed into practical guidance.
The Intergovernmental Panel on Climate Change (IPCC) synthesises thousands of peer-reviewed scientific studies, producing comprehensive assessments that summarise the current state of knowledge. Its reports are not designed to persuade. Their purpose is to evaluate evidence, identify areas of agreement and clearly explain where uncertainty remains.
Alongside the IPCC, organisations such as Project Drawdown focus on solutions rather than diagnosis.
Project Drawdown evaluates hundreds of potential measures capable of reducing greenhouse gas emissions or increasing resilience. These include improvements in energy efficiency, expansion of low-carbon electricity generation, restoration of forests and wetlands, regenerative agriculture, electrification of transport, reductions in food waste and advances in industrial processes.
One of its most important conclusions mirrors that of many climate researchers.
There is unlikely to be a single technological solution.
Progress is more likely to result from combining multiple approaches whose effectiveness depends upon geography, economics, available infrastructure and societal priorities.
Beyond ideology
Perhaps the greatest challenge surrounding climate change is no longer scientific.
It is cultural.
In many countries, climate has become associated with political identity. As a result, scientific evidence is sometimes judged according to whether it appears to support one ideological position or another.
Science functions differently.
It asks whether observations agree with theory.
Whether competing explanations account for the evidence.
Whether new measurements reinforce or weaken previous conclusions.
The climate system has no political preference.
Atmospheric physics does not change according to election results.
Ocean heat content is unaffected by ideology.
This does not mean that science is infallible.
It means that its conclusions remain open to revision whenever better evidence becomes available.
That willingness to change in response to evidence is precisely what distinguishes science from belief.
More than a century of observations has transformed climate science into one of the most comprehensively documented fields of modern research.
Surface thermometers.
Ocean observations.
Weather balloons.
Ice cores.
Satellite missions.
Atmospheric chemistry.
Sea-level measurements.
Glacier monitoring.
Each provides only one perspective.
Together, they describe a coherent physical system whose energy balance is changing.
Current evidence indicates that the Earth has warmed significantly since the late nineteenth century and that human activities — primarily the combustion of fossil fuels and associated greenhouse gas emissions — are the dominant cause of the warming observed since the mid-twentieth century.
This conclusion should not be mistaken for the end of scientific enquiry.
Important questions remain regarding regional impacts, cloud feedbacks, future ice-sheet behaviour and the pace of adaptation required under different warming scenarios.
Science continues because those questions matter.
Yet acknowledging uncertainty should not obscure what decades of independent observation have already established.
The history of science demonstrates that confidence does not arise from unanimity.
It emerges when increasingly diverse evidence continues pointing towards the same explanation despite repeated attempts to test it.
Climate science has now reached that stage.
Whether societies choose to accelerate mitigation, invest more heavily in adaptation or pursue different combinations of both will remain matters of public policy.
The physical evidence, however, exists independently of those choices.
Science rarely offers absolute certainty.
What it offers instead may be even more valuable: a disciplined method for distinguishing, progressively and transparently, between what we believe and what the evidence is prepared to support.
Further information
Intergovernmental Panel on Climate Change (IPCC)
World Meteorological Organization (WMO)
NASA Climate
National Oceanic and Atmospheric Administration (NOAA)
Copernicus Climate Change Service (C3S)
World Glacier Monitoring Service (WGMS)
National Snow and Ice Data Center (NSIDC)
Project Drawdown
Images credits: NASA
